Sun Hua-Jun, Luo Man-Li, Zhou Xin, Zhou Qian, Sun Yang-Yang, Ge Wan-Ying, Yao Miao-Miao, Ji Shu-Juan
Department of Food Science, Shenyang Agricultural University, 110866 Shenyang, People's Republic of China.
Hortic Res. 2020 Sep 1;7:136. doi: 10.1038/s41438-020-00356-3. eCollection 2020.
Refrigeration is commonly used to extend the storage life of "Nanguo" pears, but fruit in long-term refrigeration is prone to peel browning, which is related to membrane lipid degradation. To determine the mechanism of membrane lipid degradation, we identified two R2R3-MYB transcription factors (TFs), PuMYB21 and PuMYB54, from "Nanguo" pears, which were notably expressed in response to cold stress and during the peel-browning process. The results from yeast one-hybrid, electrophoretic mobility shift, and transient expression assays indicated that both PuMYB21 and PuMYB54 directly bind to the promoter of (a key enzyme catalyzing the hydrolysis of membrane phospholipids) and activate its expression, which probably enhances the degradation of membrane phospholipids and eventually results in peel browning. Moreover, the overexpression of PuMYB21 and PuMYB54 can greatly activate the transcription of endogenous in both "Nanguo" pear fruits and calli, and their silencing can inhibit its transcription. Furthermore, yeast two-hybrid, bimolecular fluorescence complementation, and pull-down assays verified that PuMYB21 interacts with PuMYB54 to enhance the expression of . In summary, we demonstrate that PuMYB21 and PuMYB54 may have roles in membrane lipid metabolism by directly binding to the downstream structural gene during the low temperature-induced peel browning of "Nanguo" pears.
冷藏常用于延长“南果”梨的贮藏寿命，但长期冷藏的果实容易出现果皮褐变，这与膜脂降解有关。为了确定膜脂降解的机制，我们从“南果”梨中鉴定出两个R2R3-MYB转录因子（TFs），即PuMYB21和PuMYB54，它们在低温胁迫和果皮褐变过程中显著表达。酵母单杂交、电泳迁移率变动和瞬时表达分析结果表明，PuMYB21和PuMYB54均直接结合（一种催化膜磷脂水解的关键酶）的启动子并激活其表达，这可能增强了膜磷脂的降解并最终导致果皮褐变。此外，PuMYB21和PuMYB54的过表达能极大地激活“南果”梨果实和愈伤组织中内源性的转录，而它们的沉默则会抑制其转录。此外，酵母双杂交、双分子荧光互补和下拉分析证实，PuMYB21与PuMYB54相互作用以增强的表达。总之，我们证明，在低温诱导的“南果”梨果皮褐变过程中，PuMYB21和PuMYB54可能通过直接结合下游结构基因在膜脂代谢中发挥作用。
